Motor control center units with retractable stabs and interlocks

ABSTRACT

Motor control centers have units or buckets with one or more sliding shutters that controllably block access to a stab isolation port based on position of the operator disconnect handle using attached cams that slide the shutter right and left. A front panel of the unit or bucket may also be configured to pivot out about a long axis associated with a bottom long side thereof.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/006,949 filed Jun. 13, 2018, which is a continuation of U.S. patentapplication Ser. No. 15/352,825 filed Nov. 16, 2016, now U.S. Pat. No.10,020,642, issued Jul. 10, 2018, which is a continuation of U.S. patentapplication Ser. No. 14/318,971 filed Jun. 30, 2014, now U.S. Pat. No.9,531,169, issued Dec. 27, 2016, the contents of which are herebyincorporated by reference as if recited in full herein.

FIELD OF THE INVENTION

The present invention relates to motor control systems and moreparticularly to motor control center units.

BACKGROUND OF THE INVENTION

As is known to those of skill in the art, Motor Control Centers (MCC)can include cabinets or enclosures that hold multiple, typicallymodular, bucket assemblies of various sizes. See, e.g., U.S. Pat. No.4,024,441, the contents of which are hereby incorporated by reference asif recited in full herein. Eaton Corporation has recently introduced aMCC product line with compact bucket assemblies that conveniently pluginto a slot or space in an MCC cabinet. The product is sold under theproduct name, Freedom 2100 MCC. See also, U.S. Patent ApplicationPublication Serial Number US2013/0077210, the contents of which arehereby incorporated by reference as if recited in full herein.

Motor control centers are used, for example, in some commercial andindustrial applications to distribute electrical power to a variety ofloads (e.g., without limitation, relatively high power electricalmotors, pumps, and other loads).

The bucket assemblies (also known as “buckets” or “units”) can includehandles that are disposed on the front door. The handle can be a rotaryhandle configured to convert the rotary motion of the rotary handle tothe linear or translational motion of a circuit breaker linear actionlever. See, e.g., U.S. Pat. Nos. 6,194,983 and 7,186,933, the contentsof which are incorporated by reference as if recited in full herein. Thehandle is typically mounted parallel with the plane of the faceplate ofthe molded case circuit breaker, but spaced outwardly from it by thedepth of the handle mechanism. Usually, a series of linkages areutilized to interconnect the rotary motion of the rotary handle to thelinear motion of the circuit breaker handle or lever.

FIG. 1, for example, shows a portion of a prior art motor control center100. The motor control center 100 includes a multi-compartment enclosure12 for receiving a plurality of motor control units 10. Typically, eachbucket 10 is a removable, pull-out unit that has a respective door 22(which may be under a front panel). The door 22 is typically coupled tothe housing 12 by hinges 28 (shown in phantom line drawing in FIG. 1) topermit access to motor control components of the bucket 10 while it isinstalled in the enclosure 12. For example and without limitation, thedoor 22 permits access to a circuit breaker assembly 30, a stabindicator 32, a shutter indicator 34, and a line contact actuator 36.When the bucket 10 is fully installed and electrically connected, auser-operator may operate a disconnect handle 20 h. In a de-energizedstate of the motor control center 100, the user-operator may operate anisolation feature by moving a slide 140 and inserting crank 42 throughan access portal or hole 43 in the door 22 to access the line contactactuator 36 to move a number of line contacts (see, for example, stabcontacts 46,48,50 of the prior art bucket 10 of FIG. 2) to an isolatedposition out of (see FIG. 2) electrical contact with power lines orbuses of the motor control center 100. Motor control centers and unitstherefore (also sometimes called “subunits”) are described in greaterdetail, for example, in commonly assigned U.S. Patent ApplicationPublications 2009/0086414, 2008/0258667, 2008/0023211 and 2008/0022673,which are hereby incorporated herein by reference.

Despite the above, there remains a need for alternate bucketconfigurations.

SUMMARY OF EMBODIMENTS OF THE INVENTION

Embodiments of the invention provide units with a sliding shutter toprevent access to a portal for an isolation feature which allows auser-operator to retract stabs in the units.

Embodiments of the invention provide buckets with portal shutters havingseparately, independently operative shutter movement for dual feederunits.

The shafts of operator mechanisms attached to a handle can be attachedto interlocks that have a cam configured to slide a shutter to open andclose access to an electrical portal associated with a retractable stab.

Embodiments of the invention are directed to bucket sub-assembliesconfigured to control access to a stab portal of a bucket unit. Thesub-assemblies include first and second spaced apart operator disconnecthandles, the first operator disconnect handle attached to a firstinwardly extending shaft that holds a first cam, the second operatordisconnect handle attached to a second inwardly extending shaft thatholds a second cam. The first and second cams are configured toindependently rotate. The first and second cams rotate in response torotation of a corresponding operator disconnect handle. Thesub-assemblies also include at least one shutter in communication withthe first and second cams. The at least one shutter has a shutter portaland the at least one shutter is configured to cooperate with the firstand second cams to laterally slide to a position that misaligns theshutter portal with a stab isolation portal to block access to the stabisolation portal when the first and/or second operator disconnect handleis in the ON position associated with conduction.

The first and second cams can each comprise first and second drivesegments, one of which slides the at least one shutter one direction andone of which slides the at least one shutter in an opposite direction.

The drive segments can include arms that reside angularly apart betweenabout 45-135 degrees.

The arms can extend straight out from the shaft and are orthogonal toeach other.

The bucket sub-assemblies can include a front panel holding the firstand second operator disconnect handles. The front panel can be a singlepanel or side-by-side dual sub-panels that are attached along innershort sides thereof to be able to pivot outward together. The singlepanel or dual sub-panels can be pivotably attached to a unit housing topivot outward along a long axis associated with a long bottom side ofthe front panel.

The first and second operator disconnect handles can be right and leftoperator disconnect handles. The bucket sub-assemblies can include rightand left interlock linkages. The right interlock linkage can include alink with one end portion attached to the first shaft and pivotablyattached to a right lever at an opposing end portion. The left interlocklinkage can include a link with one end attached to the second shaft atone end portion and pivotably attached to a left lever at an opposingend portion. The links can extend straight outward from respective firstand second shafts. The right lever can have and end portion that isconfigured to extend out of a right sidewall of a unit housing when theright operator disconnect handle is in the ON position and the leftlever can have an end portion that is configured to extend out of a leftsidewall of the unit housing when the left operator disconnect handle isin the ON position.

The at least one shutter can be a single shutter. The first and secondoperator disconnect handles can be right and left operator disconnecthandles. The right and left cams can be configured to slide the singleshutter right and left independently of each other.

The at least one shutter can be a single shutter. The first and secondcams can be configured to slide the single shutter independently of eachother.

The first and second operator handles can be held by a front panel thatis configured to pivot outward from hinges residing at a lower opposinglong end portions thereof, and wherein the front panel engages a unitinterlock to controllably lock and unlock the interlock to allow thepivoting movement only when there is non-conduction.

Other embodiments are directed to bucket assemblies. The bucketassemblies include a unit housing having a front panel and opposinglaterally spaced apart sidewalls extend rearward of the front panel ofthe unit housing. The bucket assemblies also include a right operatordisconnect handle on the front of the unit housing and attached to aright inwardly extending shaft. The right shaft holds a right camconfigured to rotate in response to rotation of the right operatordisconnect handle. The bucket assemblies also include a left operatordisconnect handle on the front of the unit housing and attached to aleft inwardly extending shaft. The left operator disconnect handle islaterally spaced apart from the right operator disconnect handle. Theleft shaft holds a left cam configured to rotate in response to rotationof the left operator disconnect handle. The bucket assemblies alsoinclude at least one shutter in communication with the right and/or leftcam whereby the at least one shutter slides to the right and left inresponse to contact with the right and/or left cam. The bucketassemblies also include a stab isolation portal residing above the rightand left shafts of the right and left operator disconnect handles. Theat least one shutter has a shutter portal. The at least one shutter isconfigured to have a position that misaligns the shutter portal with thestab isolation portal to block access to the stab isolation portal wheneither of the right and left operator disconnect handles is in the ONposition associated with conduction.

The at least one shutter is a single shutter and the right and left camsare configured to slide the single shutter independently of each other.

The bucket assemblies can also include a right interlock linkageattached to the right shaft and a left interlock linkage attached to theleft shaft, each configured to rotate with respective right and leftshafts.

The bucket assemblies can include a right feeder or starter held in theunit housing in communication with the right operator disconnect handleand a left feeder or starter held in the unit housing in communicationwith the left operator disconnect handle.

The cam can include arms that reside angularly apart between about45-135 degrees.

The at least one shutter can include a single shutter or two adjacentshutters. The the single shutter or the two shutters can be configuredwith left and right cam followers residing on lower portions of thesingle shutter or on lower portions of the two shutters.

The bucket assemblies can include right and left interlock linkages,each with a link attached to a respective shaft at one end portion andpivotably attached to a lever at an opposing end portion. The link canextend straight outward from a respective shaft. The lever attached tothe right shaft has an end portion that can be configured to extend outof a right sidewall of the bucket assembly when the right operatordisconnect handle is in the ON position and the lever attached to theleft shaft has an end portion that can be configured to extend out of aleft sidewall of a unit housing of the bucket assembly when the leftoperator disconnect handle is in the ON position.

The front panel can be a single panel that extends between thesidewalls.

The front panel can be configured as two adjacent sub-panels that areattached at inner sides thereof to be able to pivot outwardly in concertalong the long axis.

Still other embodiments are directed to a motor control center (MCC).The MCC includes a housing with first and second sidewalls defining anenclosure with a plurality of compartments. The compartments areconfigured to removably receive a plurality of units, at least one ofthe units includes: (a) a unit housing having a front and opposinglaterally spaced apart sidewalls that extend rearward of the front ofthe unit housing; (b) at least one operator disconnect handle on thefront of the housing and attached to an inwardly extending shaft, theshaft holds a cam configured to rotate in response to rotation of theoperator disconnect handle, the cam includes first and second arms thatextend straight out from the shaft and that reside angularly spacedapart between about 45-135 degrees; (c) at least one shutter in serialcommunication with the first and second arms of the cam whereby the atleast one shutter slides right and left in response to a follower thatcontacts the first and second arms of the cam; and (d) a stab isolationportal residing above the shaft of the operator disconnect handle. Theshutter has a shutter portal. The shutter is configured to have aposition that misaligns the shutter portal with the stab isolationportal to block access to the stab isolation portal when the at leastone operator disconnect handle is in the ON position associated withconduction.

The front of the unit housing can include a pilot panel segment orsub-panel holding a plurality of pilot devices laterally spaced apartfrom the at least one operator disconnect handle.

The at least one operator disconnect handle can include a right operatordisconnect handle with a right shaft and right cam and a left operatordisconnect handle with a left shaft and left cam. The right and leftcams are configured to slide the at least one shutter right and leftindependently of each other.

The at least one operator handle can be held by a front panel attachedto the unit housing. The front panel can be configured to pivot outwardfrom hinges residing at a lower opposing long end portions thereof. Thefront panel engages a unit interlock attached to the unit housing tocontrollably lock and unlock the front panel to allow the pivotingmovement only when there is non-conduction.

Other embodiments include methods of controlling access to a stabisolation portal of a bucket. The methods include rotating an externallyaccessible operator disconnect handle of a bucket or unit to an ONposition, the operator disconnect handle attached to an inwardlyextending shaft, the shaft holding a laterally outwardly extendinginterlock linkage and a cam. In response to the rotation of the operatordisconnect handle, (i) an outer end portion of the interlock linkageextends out through an aperture in a sidewall of the bucket or unit and(ii) the cam forces a shutter to slide left or right to block access toa stab isolation access portal associated with a retractable stab.

The bucket can be a dual feeder or starter bucket with right and leftoperator disconnect handles, each having respective shafts with the camand interlock linkage. The rotating can be carried out so that the camsof each shaft move the shutter independently of the other and areconfigured to slide the shutter to a position that blocks access to thestab isolation access portal unless both the right and left operatorhandles are in an OFF position associated with non-conduction.

Still other embodiments are directed to bucket assemblies. Theassemblies include: a unit housing; and a front panel holding either (i)first and second operator disconnect handles or (ii) at least oneoperator disconnect handle with a pilot panel. The front panel is asingle panel or side-by-side dual sub-panels that are attached alonginner short sides thereof to be able to pivot outward together. Thesingle panel or dual sub-panels are pivotably attached to the unithousing to pivot outward along a long axis associated with a long bottomside of the front panel. The front panel engages a unit interlockattached to the unit housing to controllably lock and unlock the frontpanel to allow the pivoting movement away from the unit housing onlywhen there is non-conduction.

The first and second operator disconnect handles are right and leftoperator disconnect handles. The bucket sub-assembly can include rightand left interlock linkages, the right interlock linkage comprising alink with one end portion attached to the first shaft and pivotablyattached to a right lever at an opposing end portion and the leftinterlock linkage comprising a link with one end attached to the secondshaft at one end portion and pivotably attached to a left lever at anopposing end portion. The links extend straight outward from respectivefirst and second shafts. The right lever has an end portion that isconfigured to extend out of a right sidewall of a unit housing of abucket assembly when the right operator disconnect handle is in the ONposition and the left lever has an end portion that is configured toextend out of a left sidewall of a unit housing of a bucket assemblywhen the left operator disconnect handle is in the ON position.

Still other embodiments are directed to a bucket assembly that includes:(a) a unit housing having a front and opposing laterally spaced apartsidewalls extend rearward of the front of the unit housing; (b) at leastone operator disconnect handle on the front of the unit housing andattached to an inwardly extending shaft, the shaft holds (i) at leastone cam configured to rotate in response to rotation of a respectiveoperator disconnect handle and (ii) an interlock linkage that pivots asthe shaft rotates to extend a sufficient distance to extend through anaperture in the sidewall of the unit housing and retract to be insidethe unit housing; (c) at least one shutter in communication with the atleast one cam whereby the at least one shutter slides to the right andleft in response to contact with the cam; and (d) a stab isolationportal residing above the shaft of the at least one operator disconnecthandle. The at least one shutter has a shutter portal. The at least oneshutter is configured to have a position that misaligns the shutterportal with the stab isolation portal to block access to the stabisolation portal when the at least one operator disconnect handle is inthe ON position associated with conduction.

Further features, advantages and details of the present invention willbe appreciated by those of ordinary skill in the art from a reading ofthe figures and the detailed description of the preferred embodimentsthat follow, such description being merely illustrative of the presentinvention.

It is noted that aspects of the invention described with respect to oneembodiment, may be incorporated in a different embodiment although notspecifically described relative thereto. That is, all embodiments and/orfeatures of any embodiment can be combined in any way and/orcombination. Applicant reserves the right to change any originally filedclaim or file any new claim accordingly, including the right to be ableto amend any originally filed claim to depend from and/or incorporateany feature of any other claim although not originally claimed in thatmanner. These and other objects and/or aspects of the present inventionare explained in detail in the specification set forth below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial front perspective view of an exemplary prior artMotor Control Center (MCC).

FIG. 2 is a top perspective view of an example of a prior art unit ofthe MCC.

FIG. 3 is a front perspective view of an exemplary unit with a dualfeeder configuration according to embodiments of the present invention.

FIG. 4 is a left side perspective view of another exemplary unit with adual feeder configuration according to embodiments of the presentinvention.

FIGS. 5A and 5B are front views of exemplary “ON” (FIG. 5A) and “OFF”(FIG. 5B) operational positions of the handle shown in FIG. 4 for theassociated internal disconnect according to embodiments of theinvention.

FIG. 5C is a front perspective view of the handle shown in FIGS. 5A and5B illustrating an extended lockable configuration according toembodiments of the present invention.

FIG. 6 is a front perspective view of yet another exemplary unit with arotary disconnect on one side and a plurality of control devices on theother side according to embodiments of the present invention.

FIG. 7 is a front perspective view of the unit shown in FIG. 6 withoutthe top cover illustrating a retractable stab configuration and portalinterlock according to embodiments of the present invention.

FIG. 8 is a front perspective view of a unit similar to that shown inFIG. 6, but with a different handle and control device panel layoutaccording to embodiments of the present invention.

FIG. 9 illustrates examples of a device panel for different pilotcontrol items which can vary by product and/or customer according toembodiments of the present invention.

FIG. 10 is a front perspective view of an exemplary unit shown with theexternal cover over the racking (stab isolation) portal omitted toillustrate a sliding shutter that overlies the racking portal and thatcooperates with an interlock mechanism according to embodiments of thepresent invention.

FIG. 11 is a front view perspective view of a unit with a dual feederconfiguration as shown in FIG. 3, but with the front cover/panelsomitted to illustrate exemplary interlocks according to embodiments ofthe present invention.

FIG. 12A is a front perspective view of an exemplary right hand linkage,illustrating the configuration of the linkage when the handle is in anOFF position according to embodiments of the present invention.

FIG. 12B is a front perspective view of the exemplary right handlinkage, illustrating the configuration of the linkage when the handleis in an ON position according to embodiments of the present invention.

FIG. 13A is a front perspective view of an exemplary left hand breakerlinkage, illustrating the configuration of the linkage when the handleis in an OFF position according to embodiments of the present invention.

FIG. 13B is a front perspective view of the exemplary left hand breakerlinkage, illustrating the configuration of the linkage when the handleis in an ON position according to embodiments of the present invention.

FIGS. 14A and 14B are schematic illustrations of alternative shutterconfigurations according to embodiments of the present invention.

FIG. 15 is a bottom perspective view of internal components of anexemplary unit according to embodiments of the present invention.

FIG. 16 is a side perspective view of the unit shown in FIG. 8,illustrating the handle sub-panel and the pilot device sub-panel joinedtogether to be able to pivot outward and inward in concert and engageunit interlocks according to embodiments of the present invention.

FIG. 17 is a side perspective view of the unit shown in FIG. 7, alsoillustrating the handle panel and the pilot device panel as a commonpanel to pivot outward and inward in concert and engage unit interlocksaccording to embodiments of the present invention.

FIG. 18 is a side perspective view of a unit illustrating a left handlinkage in the unit and a unit interlock which engages the front hingedpanel shown in FIGS. 16 and 17, for example, and which is controlled bya controller for interlock control according to embodiments of thepresent invention.

FIG. 19 is a partial exploded view of an exemplary unit illustratingcomponents of an exemplary operator mechanism and fuse system accordingto some embodiments of the present invention.

FIG. 20 is a flow chart of exemplary operation of a unit with aninterlock associated with a portal shutter according to embodiments ofthe present invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The present invention now will be described more fully hereinafter withreference to the accompanying drawings, in which illustrativeembodiments of the invention are shown. Like numbers refer to likeelements and different embodiments of like elements can be designatedusing a different number of superscript indicator apostrophes (e.g., 10,10′, 10″, 10″′).

In the drawings, the relative sizes of regions or features may beexaggerated for clarity. This invention may, however, be embodied inmany different forms and should not be construed as limited to theembodiments set forth herein; rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the invention to those skilled in the art.

It will be understood that, although the terms first, second, etc. maybe used herein to describe various elements, components, regions, layersand/or sections, these elements, components, regions, layers and/orsections should not be limited by these terms. These terms are only usedto distinguish one element, component, region, layer or section fromanother region, layer or section. Thus, a first element, component,region, layer or section discussed below could be termed a secondelement, component, region, layer or section without departing from theteachings of the present invention.

Spatially relative terms, such as “beneath”, “below”, “lower”, “above”,“upper” and the like, may be used herein for ease of description todescribe one element or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is turned over, elements described as “below” or “beneath” otherelements or features would then be oriented “above” the other elementsor features. Thus, the exemplary term “below” can encompass both anorientation of above and below. The device may be otherwise oriented(rotated 90° or at other orientations) and the spatially relativedescriptors used herein interpreted accordingly.

The term “about” refers to numbers in a range of +/−20% of the notedvalue.

As used herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless expressly stated otherwise. Itwill be further understood that the terms “includes,” “comprises,”“including” and/or “comprising,” when used in this specification,specify the presence of stated features, integers, steps, operations,elements, and/or components, but do not preclude the presence oraddition of one or more other features, integers, steps, operations,elements, components, and/or groups thereof. It will be understood thatwhen an element is referred to as being “connected” or “coupled” toanother element, it can be directly connected or coupled to the otherelement or intervening elements may be present. As used herein, the term“and/or” includes any and all combinations of one or more of theassociated listed items.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of this specification andthe relevant art and will not be interpreted in an idealized or overlyformal sense unless expressly so defined herein.

In the present disclosure, the terms “bucket” or “unit” are usedinterchangeably and are intended to mean a motor control center unitthat may be configured to be a removable modular unit capable of beinginstalled behind individual or combined sealed doors on the motorcontrol center enclosure. The unit may contain various motor control andmotor protection components such as motor controllers, starters,contactor assemblies, overload relays, circuit breakers, motor circuitprotectors, various disconnects, and similar devices for electricmotors. The unit is configured to connect to a common power bus of themotor control center and conduct supply power to the line side of themotor control devices for operation of motors or feeder circuits.

As discussed before, units may be configured as “starter units” forsupplying power controlling electrical motors and pumps or as general“feeder units” for supplying feeder circuits. The terms “bucketassembly”, bucket” and “unit” are used interchangeably and refer to astructure (typically having sides of a protective metal shell) thatcontains either a switch with a fuse or a circuit breaker for turningpower ON and OFF to a motor, or feeder circuit, typically forcontrolling power to motor starters. As noted above, the bucket or unitcan be a feeder unit or a starter unit. The bucket can include othercomponents such as a power transformer, a motor starter to control asingle motor and PLCs (programmable logic controllers), drives and thelike. The bucket can be configured as a modular device to allow theinternal components to be assembled as a unit that can be easilyinstalled into a Motor Control Center (MCC) compartment. As is wellknown, the bucket 10 can have a bus grid with “power stabs” 46, 48, 50(FIG. 4) in the back that connect to bus bars that carry power (current)to the compartments of a vertical section in an MCC cabinet 100 (FIG.1). The bus bars are connected to larger horizontal bus bars that bringpower to the vertical sections. The horizontal bus bars are usually inthe top, but some MCC designs may have them in the center or bottom.

A “feeder unit” refers to a motor control center unit for supplyingfeeder circuits. A feeder unit may have one or more feeders or powersupply lines to supply feeder circuits or devices. A feeder unit (alsocalled a “feeder”) can have a “line side”, which refers to the side ofthe feeder configured to be directly or indirectly connected to thecommon power bus of the motor control center. A feeder can also have a“load side”, which refers to the side of the feeder configured to beconnected to and deliver current to a feeder circuit. A feeder maycomprise a circuit breaker, a fuse and disconnect switch, or anotherconfiguration. The terms “feeder circuit” and “feeder device” are usedinterchangeably and are intended to mean circuits or devices connectedto feeder units or “feeders”.

A “circuit breaker”, “breaker”, “molded case circuit breaker”, or “MCCB”is a device designed to open and close a circuit, typically allowingboth manual open and close operation and automatic circuit interruption,the latter to open a circuit under certain conditions, e.g., anover-current. The circuit breaker can be for a motor starter unit orfeeder unit, for example.

The terms “motor”, “load”, and “load device” are used interchangeablyand are intended to mean devices bearing electrical load that areconnected to and controlled by the motor control center. Load devicesare typically motors but may also be pumps or other machinery that maycomprise motors or pumps. Load devices may be connected to starterunits.

The terms “operating mechanism” and “operator mechanism” are usedinterchangeably and refer to an assembly for opening and closingseparable main contacts in a circuit breaker or for turning power ON andOFF using a switch associated with a fuse as a disconnect.

MCCs usually have a wire way for wires from respective units 10 to themotors and other loads and control wires. U.S. Patent ApplicationPublication 2013/0077210 describes an MCC with both right and left sidewireways, the contents of which are hereby incorporated by reference asif recited in full herein. The wireways are typically provided as anenclosed space in an MCC cabinet proximate but outside stacked units.MCCs can be configured in many ways. Each compartment can have adifferent height to accept different frame sizes of respective bucketassemblies or units 10, typically in about 6-inch increments. Thevertical bus can be omitted or not run through the full height of thesection to accommodate deeper buckets for larger items like variablefrequency drives. The MCC can be a modular cabinet system for poweringand controlling motors or feeder circuits. Several may be powered frommain switchgear which, in turn, gets its power from a transformerattached to the incoming line from the power company. A typical MCCcabinet is an enclosure with a number of small doors arranged in rowsand columns along the front. The back and sides are typically flat andmostly featureless. The buckets can be provided in varying sizes. Forstarter units, the size can be based on the size of the motor they arecontrolling. The bucket assembly can be configured to be relativelyeasily removable for repair, service or replacement. MCCs can haveregular starters, reversing starters, soft start, and variable frequencydrives. MCCs can be configured so that sections can be added forexpansion if needed. The buckets or units 10 of a motor control center100 can have the same or different configurations.

The terms “right side” and “left side” refer when the unit or MCC isviewed from the front, e.g., the front is associated with the unit 10orientation shown in FIGS. 3 and 4, for example, with handles 20 hfacing forward as shown in FIGS. 3 and 4. While the handles 20 h areshown as rotary handles, other handle configurations may be used,including, for example, push handles, levers and linearly moveablehandles. It is also noted that the dual feed configurations are shown asside by side arrangements, but it is contemplated that verticallyaligned handles may also or alternatively be used with the respectivedisconnects placed in the unit accordingly.

The term “compact” refers to units 10 held in a condensed configuration(package) relative to conventional units/buckets. The MCC structure orcabinet 100 (FIG. 1) can be designed to receive multiple bucket units 10ranging in various defined sizes. The units 10 can be provided inpackage or frame sizes of about 6 inches to about 72 inches (tall) withsubstantially common depth and width dimensions, known as 1X (6 inches)to 12X (72 inches) sizes. The sizes can be in single X increments, from1X, 2X, 3X, 4X, 5X, 6X, 7X, 8X, 9X, 10 X, 11X and 12X. Thus, a 5X MCCunit 10 can be about 30 inches tall. The frame sizes can be provided fora plurality of amperages, including a plurality of: 125 A, 150 A, 225 A,250 A, 400 A, 600 A, 1200 A and 2000 A, for example. A unit 10 istypically about 7 inches deep but larger or smaller sizes may beappropriate in some embodiments.

Referring now to FIGS. 3 and 4, in some embodiments, the bucket assemblyor unit 10 has a dual feeder and/or starter configuration. For theembodiments shown in FIGS. 3 and 4, the dual feeder and/or starter unit10 includes respective right and left handles 20 h attached to arespective shaft 25 of a corresponding disconnect D such as a disconnectoperator mechanism 40 (FIG. 19). The bucket assembly 10 can beconfigured for DC (direct current) or AC (alternating current)operation. The bucket assembly 10 can include a front cover 11 (FIG. 6)residing over the door 22 or panel holding the handle 20 h. The bucketassembly 10 can have a metal enclosure, frame or housing 12 withsidewalls 13.

In some embodiments, the bucket assembly 10 can comprise a molded casecircuit breaker 10C. Molded case circuit breakers are well known tothose of skill in the art, as exemplified by U.S. Pat. Nos. 4,503,408and 5,910,760, the contents of which are incorporated herein byreference as if recited in full herein. In other embodiments, the bucketassembly 10 can be configured to house a fused disconnect switch to turnpower on and off. In some embodiments, the MCC cabinet 100 (FIG. 1) canhold both a fused disconnect switch and circuit breaker type units 10and each can have a standardized rotary handle 20 h that controls theinternal components for power on/off operation.

As shown in FIGS. 3 and 4, the unit 10 includes two (typicallyside-by-side) operator handles 20 h that individually communicate withrespective internal disconnect and/or operator mechanisms 40 (FIG. 19)that, in turn, connect to an internal circuit breaker 10C or adisconnect switch 10S, respectively. The handles 20 h can be rotaryhandles. FIGS. 3 and 4 also illustrate interlock linkages 70 that extendthrough respective left and right side apertures 13 a in the sidewalls13 of the unit.

The unit 10 can be configured so that the stab S is offset to residecloser to one side of the unit, e.g., so that a left side stab 46 orright side stab 50 (and/or the center stab 48) is closer to a respectiveleft or right side of the unit 10. FIGS. 4 and 7 show the center stab 48as residing closer to the right side of the unit 10, according to someembodiments.

FIGS. 3, 4, 6, 7 and 8 illustrate that the unit 10 has a stab isolatingportal 43 residing above the handle 20 h (FIG. 6-8) or handles 20 h(FIGS. 3 and 4). The top cover of the unit 10 is not shown in FIG. 7 tomore clearly illustrate the retractable stab S.

FIG. 3 illustrates one example of tandem rotary handles 20 h while FIG.4 illustrates another exemplary embodiment of tandem rotary handles 20h. FIG. 5A illustrates an exemplary “ON” orientation/position of thehandle 20 h while FIG. 5B illustrates an exemplary “OFF” position. Thus,in operation, the pre-defined orientation of the rotary handle 20 h withrespect to operation status can provide a visual indication to auser-operator of the conduction status of the disconnect d, e.g.,breaker 10C or switch disconnect 10S (optionally with a fuse) beingON/OFF.

The term “ON” with respect to handle position/orientation refers to theassociated feeder or starter of the unit 10 having conduction with theoperator disconnect closed (circuit breaker closed or fused switch beingON/switch closed). The term “OFF” with respect to handleposition/orientation refers to the associated feeder or starter of theunit 10 having no conduction with the disconnect open (circuit breakeropen or disconnect switch OFF/switch open).

In some embodiments, if the handle 20 h is in a generally horizontalposition, i.e., with the center lever 21 straight across the front ofthe circuit breaker as shown in FIG. 5B, this orientation can be the OFFposition and can be visually used as an indication that the contacts ofthe circuit breaker are open and that current is blocked. If the handle20 h is rotated from the orientation shown in FIG. 5A, e.g., rotated 90degrees (typically clockwise from the orientation in FIG. 5B), then anindication is given that the circuit contacts are closed. Where the unit10 includes a breaker 10C, the breaker trip position can be at about 45degrees mid-point between ON and OFF. However, as noted above, thehandles 20 h may have other configurations and are not required to berotating handles and may use other angular orientations for ON and/orOFF.

The embodiment shown in FIG. 4 can be configured to have a “push” to popout configuration as shown in FIG. 5C whereby an aperture 20 a isexposed to allow a physical lock to be attached to an end of an arm 21of the handle 20 h. For further description of this exemplary handleconfiguration, see, U.S. patent application Ser. No. 14/174,481, nowpublished as U.S. Patent Application Publication number US 2015/0221458,the contents of which are hereby incorporated by reference as if recitedin full herein.

FIG. 8 illustrates a long handle version of a handle 20 h which canprovide additional torque control for some applications. An intermediatelength handle may also be used for some embodiments (not shown).

FIGS. 6-8 illustrate units 10 with a single handle 20 h adjacent adevice or “pilot” device panel 66 configured with apertures 66 a toreceive various control input members and/or indicating light devices166 (FIG. 9). The devices 166 can include pilot control devices,indicating lights, user inputs such as push buttons and/or selectorswitches and the like. There are many different variations that can beused as is well known to those of skill in the art. While six devices166 and respective holding or receiving apertures 66 a are shown, thedevice panel 66 can be configured with more or less apertures 66 a andhold more or less control input members and/or indicating lights, forexample.

The unit 10 can have a single continuous length panel 122 that holdsboth the handle 20 h and the device panel apertures 66 a as shown inFIGS. 6 and 7. The unit 10 can be configured with the door 22 as asubpanel adjacent the separate/discrete device panel 66 as shown in FIG.8. Either embodiment may optionally be configured to engage one or moreunit interlocks 93 (FIGS. 6, 18) and may pivot outward from a bottomedge thereof as will be discussed further below.

FIG. 10 illustrates that the unit 10 can have at least one laterallyslidable shutter 75 with a portal 75 p. The shutter 75 can have slots 75s. When the portal 75 p is aligned with the isolation portal 43,external access to the portal 43 is allowed. When the portal of theshutter 75 p is left or right of the portal 43, the shutter body 75 bresides over and blocks the portal 43. FIG. 11 illustrates that theshutter 75 can reside behind a panel 76 with an aperture 43 a alignedwith the access portal 43. FIGS. 10 and 11 also illustrate that the unit10 can have a FLASHGARD interlock L typically via the top surface of theunit.

As shown by FIG. 10 and FIGS. 12A, 12B, 13A, 13B, for example, theoperator handle 20 h can be attached to an inwardly extending shaft 25.The shaft 25 can hold the interlock linkage 70 and at least one cam 80.The shaft 25 can be part of the operator disconnect mechanism D, 40(FIG. 19, for example). Each of the right and left side cams 80 can beconfigured to move the at least one shutter 75 both right to left andleft to right.

Referring to FIGS. 12A, 12B, 13A, 13B, in some embodiments, each of thecams 80 can be configured to engage a single shutter 75 that is slidleft when each handle 20 h is in the OFF position to open the shutterportal 43 by aligning portal 75 p and is slid right when each handle 20h is in the ON position to block access to the portal 43 in response tothe position of the handle 20 h.

In some embodiments, the cam 80 can reside closer the front of the unit10, e.g., closer to the handle 20 h than the linkage 70. The cam 80 canhave a plurality of radially-outwardly extending, circumferentiallyspaced apart arms 80 a (also referred to as 80 a ₁, 80 a ₂). The term“circumferentially” is used broadly to describe spacing about the shaft25, recognizing that the shaft 25 may have a non-circular shape. Atleast one of the arms 80 a pushes the at least one shutter 75 to slideleft and at least a different other at least one pushes the at least oneshutter 75 to slide right. The cam 80 may have a curvilinear camprofile, e.g., with a curvature configured with outer lobes and avalley(s) rather than or in addition to the straight arms 80 a tocontrol movement of the at least one shutter 75 (not shown).

In some embodiments, the angular spacing a between the cam arms 80 a ona respective shaft 25 can be between about 45-135 degrees, typicallyabout 90 degrees. In some embodiments, the arms 80 a are orthogonal toeach other as shown in FIG. 12A. The angular spacing can substantiallycorrespond with the angular spacing between ON and OFF for a respectivehandle 20 h orientation.

The shutter 75 can have a lower portion 75 e that can contact the cam 80when the handle 20 h is in the defined positions to move into theappropriate aligned position: (i) with the shutter portal 75 p alignedwith the portal 43 to open the access portal 43 or a misaligned positionand (ii) with the shutter portal 75 p laterally offset from the portal43 to block portal 43 access.

The lower portion 75 e can be referred to as a “cam follower”. The camfollower 75 e moves linearly and is not required to always be in contactwith the cam 80. In some embodiments, the cam 80 is configured so thatin the ON position, one arm contacts the cam follower 75 e and in theOFF position, the other arm contacts the cam follower. The cam follower75 e may extend outwardly away from a plane associated with the shutterprimary body, typically horizontally. The cam follower may extendsubstantially horizontally toward the front of the unit 10 orsubstantially horizontally toward the rear of the unit 10 and may have adifferent configuration. The cam follower 75 e can comprise ahorizontally extending protrusion or ledge that can provide assemblytolerance so as to be able to consistently engage the drive portion of arespective cam 80 held on the shaft 25 despite build tolerances. Thelateral stroke distance of the shutter 75 and/or lower portion 75 e ofthe shutter 75 in each direction, right to left and/or left to right toopen/close the access path to the portal 43 can be between about 0.25inches to about 3 inches, more typically between about 1 inch to about 2inches.

The cam 80 can be provided as a monolithic single piece body or may beprovided as discrete closely spaced components held by the shaft 25 in aproper orientation to cause the respective sliding left and rightlateral movement of the shutter 75.

The linkage 70 can pivotably attached to a short outwardly extendinglink 71 via joint 70 j with the link 71 being shorter than the lever arm72 of the linkage 70 (FIGS. 12B, 13B) and is typically shorter than thecam arms 80 a. The linkage 70 is typically fully extended (horizontal orsubstantially horizontal) in the ON position (FIG. 12B, 13B) to extendout of the sidewall 13 and is retracted so as to be pivoted downward orupward in the OFF position (FIG. 12A).

In some embodiments, a monolithic shaped (typically rigid metal) memberM can define both the short link 71 and at least one of the cam arms 80a as shown in FIGS. 12B and 13A, for example.

The shutter 75 can be provided as a single shutter that cooperates withthe right and left cams 80 of both handles 20 h as shown. Alternatively,two or more separate shutters may be provided, such as one for eachhandle 20 h and respective cam 80. For example, if two shutters areused, 75 ₁, 75 ₂, one can reside in front of the other and independentlyslide right and left in response to respective handle position 20 h(FIGS. 14A, 14B). In other embodiments, the two shutters can reside inthe same plane and laterally move to provide the access and blockingconfigurations.

The unit 10 can be configured with an interlock that ensures that theunit disconnect D (e.g., breaker) is OPEN before allowing the unit stabsS to be racked in or out, and when the disconnect D (breaker) is closed,the interlock is configured so that the stabs S must remain closed. Theracking system can be configured as a slow break contact arrangement andis not typically designed to breaker the electrical current.

FIG. 15 illustrates an internal compartment of exemplary compact dualfeeder/starter units 10 illustrating the cams 80 closely spaced to therespective handle 20 h and illustrating that one shaft 25 can be longerthan the other. FIG. 15 shows a longer shaft on the right side operatormechanism placing the operator mechanism sliders 150, 152 (FIG. 19)further back in the unit housing 10 h, closer to the back wall 10 b. Thelonger shaft 25 can have a length that is between about 3 inches toabout 5 inches. The longer shaft 25 can be between 1.5-10 times (e.g.,1.5×-10×) the length of the other shaft, e.g., about 1.5×, about 2×,about 3×, about 4×, about 5×, about 6×, about 7×, about 8×, about 9× orabout 10× the length of the other shaft 25. Typically the longer shaftis between about 1.5× to about 5× the length of the shorter shaft. Thelonger shaft 25 can be configured to have a primary shaft body attachedto an extension that provides the additional length or may be a unitarybody.

Referring to FIG. 16, in some embodiments the disconnect handle 20 h onsub-panel and/or door 22 and the device sub-panel 66 can be attached atthe inner sides 22 i, 66 i to be able to pivot outwardly in concert viajoints 66 j, 22 j, for example. Referring to FIG. 17, in someembodiments, the unit 10 can have a long (single) panel 122 that holdsthe handle 20 h and the pilot devices/components 166 and can beconfigured to pivot outward. Typically, the pivot attachment includesouter lower pivot joints 122 j at the bottom corner portions of the unit10 as shown in FIG. 17. With the configurations shown in FIGS. 16 and17, the hinged panel 122 or attached sub-panels 66, 22, can beinterlocked with the unit interlock 93 as shown in FIG. 18. The unitinterlock 93 can be in communication with an electronic controller 193that controls the release or the interlock 93. The interlock 93 mayinclude an automated clamp or latch 93 c that holds the lower end of thepanel 122 or sub-panels 22 and 66, and may include a latch 93 l thatextends out of the sidewall 13 to prevent the panel(s) from pivotingwhen the interlock is engaged.

As shown in FIG. 19, the unit 10 can include a disconnect D such as amolded case circuit breaker (MCCB) 10C or disconnect switch 10S, one orboth of which can be operated by an internal operating handle mechanism40 commonly called the “op-mech” or “operator mechanism” or “disconnectoperator”. The disconnect switch 10S can include an integrated fuse ormay be connected to a fuse, in some embodiments. This op-mech 40 can beconfigured to mount over the lever 190, e.g., a breaker's integral leverand/or an ON/OFF switch lever of disconnect switch. The op-mech 40allows a user to operate the circuit breaker 10C or switch 10S with thedoor 22 of the motor control center unit 10 closed. The door 22 and/orhandle 20 h itself can include visual indicia I (FIGS. 5A/5B/5C), e.g.,text and/or color, that identifies an operational status by position,e.g., Reset “R”, OFF, TRIPPED and ON. The TRIPPED indicia may be omittedfor fuse systems. It is noted that for ease of discussion, the dualfeeders are used by way of example. However, a respective feeder can bereplaced with a starter and any unit 10 can include two startercircuits, two feeder circuits or a starter and a feeder, for example.

For a circuit breaker configuration, the handle 20 can move betweencircuit breaker conduction to circuit breaker non-conduction. Where arotating handle is used, typically, there is about a 90° rotation fromconduction to non-conduction (“OFF” to “ON”) but other definedrotational stroke distances may be used including, for example, about 45degrees, about 120 degrees, or about 180 degrees. For a fuseddisconnect, a similar rotation can be used to cause the ON/OFF.

As shown in FIG. 19, for example, the operator mechanism 40 can includea drive gear 142, a pinion gear 144, and an operator rack gear 146.Generally summarized, the handle 20 h via shaft 25 is keyed to interfacewith the rotary drive gear 142. Drive gear 142 interacts mechanicallywith pinion gear 144. Pinion gear 144 also interacts with the linearlytranslating moveable rack 146. Consequently, as the handle 20 h rotates,because it is interlocked with the drive gear 142, the drive gear 142rotates on its axis, thus rotating the pinion gear 144, which thenlinearly moves the rack 146. The rack 146 then moves the operator slider152 over operator base 150 which moves to trip lever 190 as the handle20 h moves. The operator base 150 can be stationary and affixed to aninner housing. The base 150 can have a horizontally oriented elongateslot 150 s that is aligned with a smaller slot 152 s in the operatorslider 152. The slots 150 s, 152 s cooperate to hold lever 190 (toggle)and when the operator slider with slot 152 s moves to the right (basedon rotation of the handle 20 h, for example), this moves the lever 190to the right along the path defined by slot 150 s. It is noted that thelever 190 (also known as a toggle) can move laterally as shown or thecircuit breaker or fuse switch may be oriented to move vertically.

The base 150 and cooperating slider 152 can be provided in differentsizes with different length and width slots 150 s to accommodate smallerand larger toggles or switches 190 associated with frames of differentsizes/amperage rating.

For fused switch disconnects, the gear 142 in communication with a rackgear 146 may optionally be configured to move up and down or orthogonalto the rack gear 146. This movement can engage and move a fuse switchlever or input, up and down for ON/OFF operation. Exemplary fuses areFUSETRON™ 600V Class RK5 fuses (BU-SB13729) available from CooperBussmann Company, St. Louis, Mo. However, the design is flexible and canaccommodate other fuses including those in different classes. Foradditional description of an example of an operator mechanism andcomponents thereof for fused disconnects, see, e.g., U.S. ProvisionalApplication Ser. No. 61/890,495, now published as U.S. PatentApplication Publication number US 2015/0103472, the contents of whichare hereby incorporated by reference as if recited in full herein.

Referring again to FIG. 19, for units 10 with circuit breakers 10C, theoperating mechanism 40 can also include a trip assist spring 143 that isin communication with the rack gear 146 to assist the handle 20 h tomove to a consistent OFF position when the circuit breaker is tripped.For additional description of an example of an operator mechanism andcomponents thereof, see, e.g., U.S. Provisional Application Ser. No.61/890,495, now published as U.S. Patent Application Publication numberUS 2015/0103472, the contents of which are hereby incorporated byreference as if recited in full herein.

FIG. 20 is a flow chart of exemplary operations that can be used toprovide portal access using at least one sliding shutter. An externallyaccessible operator handle of a bucket or unit attached to an inwardlyextending shaft and holding a laterally outwardly extending interlocklinkage and a cam can be rotated to move to an ON (OPERATOR DISCONNECTCLOSED) or OFF (OPERATOR DISCONNECT OPEN) position (block 300). Theoperator handle can be rotated to the ON position to (i) extend an endportion of the interlock linkage through an aperture in a sidewall ofthe bucket and (ii) position the cam to force a shutter to slide left orright to block access to an access portal associated with control of aretractable stab (block 310).

The cam can comprise first and second outwardly extending arms, the armsbeing (circumferentially) spaced apart about the shaft (block 303). Thespacing can be about 90 degrees. The angular spacing can correspond withthe angular spacing between ON and OFF for a respective handle 20 horientation.

The bucket can be a dual starter and/or feeder with adjacent right andleft operator handles, each having the shaft with a respective linkageand cam so as to have a right shaft, right linkage and right cam, and aleft shaft, left linkage and left cam (block 305).

The rotating can be carried out so that when the left disconnect isclosed (handle in the ON position), the left shutter covers access tothe portal and when the right disconnect is closed (handle in the ONposition), the right shutter covers access to the portal (block 307).

The right and left cams can contact respective linearly movable rightand left followers that contact the portal shutter to slide the shutterand the cam followers so that the cam followers operate independently ofeach other (block 309).

The right and left cam followers can operate independently of each otherto more a common shutter or move two shutters to block the stabisolation access portal 43. Moving either disconnect handle 20 h to theopen position OPEN can cause the shutter to open the portal 43. Bothdisconnect handles 20 h can be required to be OPEN before the shutterportal 75 is aligned with the stab isolation portal 43 to allow accessto the portal 43.

The foregoing is illustrative of the present invention and is not to beconstrued as limiting thereof. Although a few exemplary embodiments ofthis invention have been described, those skilled in the art willreadily appreciate that many modifications are possible in the exemplaryembodiments without materially departing from the novel teachings andadvantages of this invention. Accordingly, all such modifications areintended to be included within the scope of this invention. Therefore,it is to be understood that the foregoing is illustrative of the presentinvention and is not to be construed as limited to the specificembodiments disclosed, and that modifications to the disclosedembodiments, as well as other embodiments, are intended to be includedwithin the scope of the invention.

That which is claimed is:
 1. A bucket assembly, comprising: a unithousing having laterally spaced apart right and left sidewalls; anoperator handle coupled to the unit housing; an interlock member coupledto the operator handle and held in the unit housing, wherein theinterlock member is configured to extend and retract, wherein, whenextended, the interlock member extends out an aperture in at least oneof the right or left sidewalls of the unit housing; a retractable powerstab assembly comprising retractable power stabs held by the unithousing, wherein the retractable power stabs are configured to be ableto extend out of a rear of the unit housing when in an extendedposition; and a shutter assembly in the unit housing comprising ashutter movable between a blocked position where access to theretractable power stab assembly is blocked and an unblocked positionwhere access to the retractable power stab assembly is permitted,wherein the shutter assembly is coupled to the operator handle and isconfigured to move the shutter to the blocked position when the operatorhandle is moved to a first position and move the shutter to theunblocked position when the operator handle is moved to a secondposition.
 2. The bucket assembly of claim 1, wherein the interlockmember is adjacent to a shaft coupled to the operator handle.
 3. Thebucket assembly of claim 1, wherein the shutter assembly furthercomprises at least one cam coupled to the operator handle and to theshutter, wherein the at least one cam is configured to rotate in concertwith the operator handle to move the shutter to the blocked andunblocked positions.
 4. The bucket assembly of claim 3, wherein theshutter comprises a primary body that is planar and extends in avertical orientation, wherein the primary body comprises a shutterportal, wherein the shutter further comprises a side portion thatextends laterally outward from the primary body of the shutter behindthe operator handle, wherein, in operation, the at least one camcontacts the shutter and laterally slides the shutter between theblocked and unblocked positions, wherein, in the unblocked position, theshutter portal is aligned with and behind an external stab isolationaccess portal, wherein, in the blocked position, the shutter portal islaterally offset from the stab isolation access portal and blocks accessto the stab isolation access portal.
 5. The bucket assembly of claim 4,wherein the primary body of the shutter comprises at least onehorizontally oriented slot spaced apart from the shutter portal, andwherein the unit housing holds the shutter to reside above the operatorhandle and closer to a front of the unit housing than a rear of the unithousing.
 6. The bucket assembly of claim 4, wherein a side portion ofthe shutter has a height that is less than that of the primary body andcomprises a ledge that cooperably engages the at least one cam to movethe shutter between the blocked and unblocked positions, and wherein theledge is at a height that is aligned with an upper portion of the atleast one cam.
 7. The bucket assembly of claim 4, wherein the primarybody of the shutter further comprises laterally spaced apart slots thatare horizontally oriented, one of the slots on a right side of theprimary body of the shutter and another of the slots on a left side ofthe primary body of the shutter, wherein the laterally spaced apartslots reside a spaced apart distance from the shutter portal and areseparated from the shutter portal by a closed wall segment of theshutter.
 8. The bucket assembly of claim 3, wherein the at least one camhas a cam body that is parallel to a primary body of the shutter, andwherein the at least one cam has an upper portion that resides above alower edge of a side portion of the shutter.
 9. The bucket assembly ofclaim 1, wherein the operator handle is a first operator handle, thebucket assembly further comprising a second operator handle laterallyspaced apart from the first operator handle and coupled to the unithousing, and wherein the second operator handle is movable between firstand second positions.
 10. The bucket assembly of claim 9, wherein thefirst and second operator handles are both coupled to the shutter andthe shutter moves to the blocked position when either the first operatorhandle or the second operator handle is in the first position.
 11. Thebucket assembly of claim 9, further comprising a first shaft in the unithousing coupled to the first operator handle and a second shaft in theunit housing coupled to the second operator handle, wherein the shutterassembly further comprises a first cam coupled to the first shaft and asecond cam coupled to the second shaft, wherein the first and secondcams each comprise at least one drive segment that engages the shutterto slide the shutter in a first direction and a second direction, thesecond direction opposite to the first direction.
 12. The bucketassembly of claim 9, wherein the shutter is configured to move to theblocked position when the power stabs are in the extended position andeither of the first or second operator handles is in the first position.13. The bucket assembly of claim 1, wherein the shutter comprises ashutter portal in the unit housing, wherein the shutter laterally slidesright and left between aligned and misaligned positions relative to astab isolation access portal provided by the unit housing to provide theunblocked and blocked positions, wherein, when in the misalignedposition corresponding to the blocked position, the shutter portal ismisaligned with the stab isolation access portal to block access to thestab isolation access portal when the retractable power stabs are in theextended position and the operator handle is in an ON positionassociated with electric current being conducted through at least onestab of the retractable power stabs, and wherein, when in the alignedposition corresponding to the unblocked position, the shutter portalaligns with the stab isolation access portal to allow access to the stabisolation access portal when the retractable power stabs are in aretracted position and the operator handle is in an OFF positionassociated with non-electric conduction through the retractable powerstabs.
 14. The bucket assembly of claim 1, wherein the operator handleis a rotary operator handle.